The Characterization Of Random Surfaces By Speckles And Light Scattering And The Simulational Computation Of The Near-field Speckles Using Method Of Green's Function

The random surfaces are of great importance in many science and technology fields such as the growth of thin films, the fine machining, the manufacture of optical devices, and etc. Near-field optics is a new interdisciplinary subject which studies the optical phenomena within one wavelength, and it breaks free from the limitation of conventional optical resolution. This paper is concentrated on theoretical, experimental and simulational studies on the measurement of random surface and the properties of near-field light scattering and its speckle field. The whole paper is divided into four chapters.Chapter 1 gives a summary and review of the description of random surfaces and its measurements, the fundamental theories of light scattering, the statistical properties of random light fields and near-field optics.In chapter 2, Based on the principle that the half-width of the Fourier transform of a symmetrical decay function is inversely proportional to the half-width of the function itself, we derive the generic expression for the half-width of the intensity profiles scattered from the self-affine fractal random surfaces. The intensity profiles are obtained at different angles of incidence by simulating light scattering from random surfaces, and by fitting these simulated profiles with a symmetrical decay function we obtain the variation of the half-width of the corresponding profiles versus the wave vector. Based on this variation and metrical results of light scattering, the lateral correlation length ? and the roughness exponent a of a random surface sample can be extracted synchronously.Chapter 3 gives a method of image speckle contrast for the non-precalibration measurement of the root-mean-square roughness and the lateral correlation length of random surfaces with Gaussian correlation. Based on the Gaussian correlation model of random surfaces and the fundamental theories of statistical optics, we obtain the expression of image speckle contrast in the 4 / optical filtering system. In the experiment, we measureexperimentally measured curve with the derived theoretical expression we can extract simultaneously the two surface parameters. The results obtained by this method conform well to the results measured with AFM.Chapter 4 proposes a method with Green functions for the simulational generation of light scattering from random surface with arbitrary parameters, and applies this method to pinhole diffraction and near-field light scattering and speckle field. In pinhole diffraction, we obtain the law that the diffracted intensity attenuates with the distance increasing from the surface according to the negative exponent decay within sub-wavelength range. We simulate light scattering from 16 self-affine fractal surface samples with different surface parameters and different length, and then study in detail the properties of scattered intensities and the near-field speckle patterns. We also simulate the transmission of light scattering with different distance from the surface, namely the evolution of the speckle patterns from near field to far field, and discover some phenomena in near-field speckles which differ from those of the well-understood far-field speckles. Some qualitative explanations are given for the analysis of these properties and phenomena.